core: discard outbound content-length header (#8522)

Since netty version v4.1.67, content-lenght header validation will be enforced. So once grpc upgrades netty to that version or above, RPCs with invalid content-length header will fail.

Some libraries such as HTTP to gRPC adapters blindly copy all HTTP headers to gRPC metadata, but the content-length header is one of those that shouldn't be forwarded because gRPC uses different encoding. This mistake has already been in existence for a long time.

Discard outbound content-length headers in gRPC, so that users who encounter invalid content-length issue when upgrading grpc-java version on server/client side would be able to workaround by upgrading grpc-java on client/server side as well without fixing the HTTP adapter.

core/src/main/java/io/grpc/internal/ClientCallImpl.java

@@ -24,6 +24,7 @@ import static io.grpc.Contexts.statusFromCancelled;
 import static io.grpc.Status.DEADLINE_EXCEEDED;
 import static io.grpc.internal.GrpcUtil.CONTENT_ACCEPT_ENCODING_KEY;
 import static io.grpc.internal.GrpcUtil.CONTENT_ENCODING_KEY;
+import static io.grpc.internal.GrpcUtil.CONTENT_LENGTH_KEY;
 import static io.grpc.internal.GrpcUtil.MESSAGE_ACCEPT_ENCODING_KEY;
 import static io.grpc.internal.GrpcUtil.MESSAGE_ENCODING_KEY;
 import static java.lang.Math.max;
@@ -163,6 +164,7 @@ final class ClientCallImpl<ReqT, RespT> extends ClientCall<ReqT, RespT> {
       DecompressorRegistry decompressorRegistry,
       Compressor compressor,
       boolean fullStreamDecompression) {
+    headers.discardAll(CONTENT_LENGTH_KEY);
     headers.discardAll(MESSAGE_ENCODING_KEY);
     if (compressor != Codec.Identity.NONE) {
       headers.put(MESSAGE_ENCODING_KEY, compressor.getMessageEncoding());

core/src/main/java/io/grpc/internal/GrpcUtil.java

@@ -109,6 +109,9 @@ public final class GrpcUtil {
   public static final Metadata.Key<byte[]> CONTENT_ACCEPT_ENCODING_KEY =
       InternalMetadata.keyOf(GrpcUtil.CONTENT_ACCEPT_ENCODING, new AcceptEncodingMarshaller());
 
+  static final Metadata.Key<String> CONTENT_LENGTH_KEY =
+      Metadata.Key.of("content-length", Metadata.ASCII_STRING_MARSHALLER);
+
   private static final class AcceptEncodingMarshaller implements TrustedAsciiMarshaller<byte[]> {
     @Override
     public byte[] toAsciiString(byte[] value) {

core/src/main/java/io/grpc/internal/ServerCallImpl.java

@@ -20,6 +20,7 @@ import static com.google.common.base.Preconditions.checkArgument;
 import static com.google.common.base.Preconditions.checkNotNull;
 import static com.google.common.base.Preconditions.checkState;
 import static io.grpc.internal.GrpcUtil.ACCEPT_ENCODING_SPLITTER;
+import static io.grpc.internal.GrpcUtil.CONTENT_LENGTH_KEY;
 import static io.grpc.internal.GrpcUtil.MESSAGE_ACCEPT_ENCODING_KEY;
 import static io.grpc.internal.GrpcUtil.MESSAGE_ENCODING_KEY;
 
@@ -107,6 +108,7 @@ final class ServerCallImpl<ReqT, RespT> extends ServerCall<ReqT, RespT> {
     checkState(!sendHeadersCalled, "sendHeaders has already been called");
     checkState(!closeCalled, "call is closed");
 
+    headers.discardAll(CONTENT_LENGTH_KEY);
     headers.discardAll(MESSAGE_ENCODING_KEY);
     if (compressor == null) {
       compressor = Codec.Identity.NONE;

core/src/test/java/io/grpc/internal/ClientCallImplTest.java

@@ -469,6 +469,15 @@ public class ClientCallImplTest {
     assertNull(m.get(GrpcUtil.MESSAGE_ENCODING_KEY));
   }
 
+  @Test
+  public void prepareHeaders_ignoreContentLength() {
+    Metadata m = new Metadata();
+    m.put(GrpcUtil.CONTENT_LENGTH_KEY, "123");
+    ClientCallImpl.prepareHeaders(m, decompressorRegistry, Codec.Identity.NONE, false);
+
+    assertNull(m.get(GrpcUtil.CONTENT_LENGTH_KEY));
+  }
+
   @Test
   public void prepareHeaders_acceptedMessageEncodingsAdded() {
     Metadata m = new Metadata();

core/src/test/java/io/grpc/internal/ServerCallImplTest.java

@@ -17,6 +17,7 @@
 package io.grpc.internal;
 
 import static com.google.common.base.Charsets.UTF_8;
+import static io.grpc.internal.GrpcUtil.CONTENT_LENGTH_KEY;
 import static org.junit.Assert.assertEquals;
 import static org.junit.Assert.assertFalse;
 import static org.junit.Assert.assertNull;
@@ -151,6 +152,16 @@ public class ServerCallImplTest {
     verify(stream).writeHeaders(headers);
   }
 
+  @Test
+  public void sendHeader_contentLengthDiscarded() {
+    Metadata headers = new Metadata();
+    headers.put(CONTENT_LENGTH_KEY, "123");
+    call.sendHeaders(headers);
+
+    verify(stream).writeHeaders(headers);
+    assertNull(headers.get(CONTENT_LENGTH_KEY));
+  }
+
   @Test
   public void sendHeader_failsOnSecondCall() {
     call.sendHeaders(new Metadata());